This invention relates generally to gas turbine engines, and more specifically to methods and apparatus for controlling cooling air temperature in gas turbine engines.
A gas turbine engine typically includes a multi-stage axial compressor, a combustor, and a turbine. Airflow entering the compressor is compressed and directed to the combustor where it is mixed with fuel and ignited, producing hot combustion gases used to drive the turbine. To control the heat transfer induced by the hot combustion gases entering the turbine, typically cooling air is channeled through a turbine cooling circuit and used to cool the turbine.
Compressor bleed air is often used as a source of cooling air for the turbine cooling circuit. Moreover, maintaining sufficient cooling air within the gas turbine engine is critical to proper engine performance and component longevity. However, during operation the temperature of air flowing through the compressor generally increases at each stage of the compressor. As a result, compressor discharge air temperature might be too high to adequately reduce the operational temperature of the gas turbine components to the desired temperature.